Easing / Easing Functions
What is Easing / Easing Functions?
Easing functions control how fast or slow an animation speeds up and slows down, making motion feel natural and physically believable rather than robotic and mechanical.
At a glance
- Also known as
- Interpolation curvesTweening curvesMotion curvesAnimation curves
- Used for
- Making animated movement feel natural and physically groundedControlling acceleration and deceleration in UI and motion graphicsDefining the feel of character and camera movement in animationDistinguishing professional-quality animation from mechanical linear motion
- Common tools
- Animation software curve editorsCSS animation timing functionsGame engine animation systemsMotion graphics timeline tools
- Related terms
- AnimationKeyframeMotion blurFrame rateIn-betweening
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How it compares
Linear interpolation changes an animated value at a constant rate from start to end, producing movement that feels mechanical and robotic because it lacks the acceleration and deceleration present in virtually all real-world physical motion. Easing applies a curve to the rate of change, reflecting the non-linear speed profiles of objects under real physical forces. The perceptual difference between a linearly animated camera move and the same move with ease in-out applied is immediately noticeable even to viewers who cannot articulate why one feels natural and the other does not.
Think of it like…
Imagine a toy car sitting still on the floor. If you push it perfectly evenly with the exact same force the whole time, it moves at a completely steady speed that feels strange and robotic, like a machine. But if you give it a gentle push that gets stronger at first and then lets it coast to a smooth stop at the end, it moves the way real cars move: building up speed, then slowing down as it arrives. That difference between the steady robotic movement and the naturally accelerating and decelerating movement is exactly what easing does in animation. It gives animated objects the same starting and stopping behavior that real objects have in the real world, so they feel like they belong to a world with gravity and physics rather than floating around in a computer. Audiences process this intuitively, feeling well-eased animation as alive and poorly eased animation as artificial, even without knowing anything about the technical principles involved.
Pro tip
When evaluating AI-generated animation or specifying motion quality in generation prompts, think in terms of how the motion should start and stop rather than only what it should show. A camera move described as beginning slowly and accelerating smoothly before gently decelerating to rest implicitly communicates ease in-out behavior that models can interpret and apply. This approach also works when reviewing generated motion for quality: footage where movements begin and end abruptly at constant speed typically indicates missing easing that could be addressed in post-production through re-timing or speed curve adjustment.
Types and variations
- Ease in begins slowly and accelerates toward the end, useful for objects starting from rest.
- Ease out begins fast and decelerates to a stop, useful for objects arriving at a destination.
- Ease in-out combines both, accelerating at the start and decelerating at the end, the most natural-feeling general option.
- Linear easing changes at a constant rate, appropriate only for contexts where mechanical precision is intentional.
- Bounce easing overshoots the endpoint and oscillates before settling, mimicking elastic or springy physical behavior.
- Elastic easing stretches significantly past the target before snapping back, used for cartoonish or stylized motion.
- Stepped easing moves in discrete quantized jumps, used for retro, 8-bit-influenced, or deliberately mechanical aesthetics.
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Try MorphicCommon use cases
- Designing UI element transitions in apps, websites, and interactive media where the easing of buttons, panels, and menus appearing or disappearing defines the feel of the interface.
- Animating motion graphics and title sequences where the acceleration and deceleration of moving elements is a primary expressive tool.
- Defining camera movement quality in cinematic animation, where ease in-out curves give dolly and pan movements the deceleration that distinguishes smooth professional camerawork from mechanical linear motion.
- Character animation in games and film where natural movement requires easing curves that reflect the physical laws governing how bodies accelerate and stop.
- Communicating animation quality requirements to AI tools through descriptive language that implies the intended easing behavior.
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FAQs
Easing describes the mathematical curves that control how fast an animated property changes over time, defining the acceleration and deceleration profile of a motion. Proper easing makes animation feel natural and physically grounded rather than mechanical and robotic.
Ease in starts the animation slowly and accelerates toward the end, like an object building momentum from rest. Ease out starts fast and decelerates smoothly to a stop, like an object arriving at its destination. Ease in-out combines both, producing the most natural-feeling general-purpose motion curve.
Linear animation changes at a constant rate without acceleration or deceleration. Almost no physical object moves this way in the real world, as all motion is subject to forces that produce non-linear speed profiles. The brain detects the absence of natural acceleration and reads linear motion as mechanical and artificial.
Bounce easing causes the animation to overshoot its target endpoint and oscillate back and forth with diminishing amplitude before settling, mimicking the behavior of an elastic or rubbery object hitting a surface. It is used for cartoon-style, playful, or physically stylized motion.
Easing functions are used in UI animation, motion graphics, game animation, cinematic camera movement, character animation, and any context where animated values need to feel natural and physically believable. They are a foundational tool in every animation software system.
AI video generation models learn motion patterns from training data and naturally reproduce the easing characteristics present in that data. Describing motion quality in prompts using language that implies natural acceleration and deceleration helps guide models toward generating footage with appropriate easing behavior.
Ease in-out, which accelerates at the start and decelerates at the end of the motion, is the most commonly used general-purpose easing function in animation. It produces the smoothest, most natural-feeling motion for the widest range of animated elements.
Stepped easing moves an animated value in discrete quantized jumps rather than a smooth continuous curve, producing a staircase-like motion pattern. It is used for retro, pixel art, or deliberately mechanical aesthetics where smooth interpolation would be inappropriate.
